Summary: Genetic divergence of the seminal signalħreceptor
system in houseŻies: the footprints of sexually
antagonistic coevolution?
Jose¨ A. Andre¨ s*
and GÎran Arnqvist
Department of Ecology and Environmental Science, Animal Ecology, University of UmeÔ, SE-901 87 UmeÔ, Sweden
To understand fully the signi˘cance of cryptic female choice, we need to focus on each of those post-
mating processes in females which create variance in ˘tness among males. Earlier studies have focused
almost exclusively on the proportion of a female's eggs fertilized by diĦerent males (sperm precedence).
Yet, variance in male postmating reproductive success may also arise from diĦerences in ability to
stimulate female oviposition and to delay female remating. Here, we present a series of reciprocal mating
experiments among genetically diĦerentiated wild-type strains of the house£y Musca domestica. We
compared the eĦects of male and female genotype on oviposition and remating by females. The genotype
of each sex aĦected both female oviposition and remating rates, demonstrating that the signal^receptor
system involved has indeed diverged among these strains. Further, there was a signi˘cant interaction
between the eĦects of male and female genotype on oviposition rate. We discuss ways in which the
pattern of such interactions provides insights into the coevolutionary mechanism involved. Females in our
experiments generally exhibited the weakest, rather than the strongest, response to males with which they
are coevolved. These results support the hypothesis that coevolution of male seminal signals and female
receptors is sexually antagonistic.